I'm glad you are having success with your wife. I hope it is continuing.
I think I have an answer to your original question, though.
Quote: How does one generate passion where none exists?
I would say if there is no passion, then there is very little to no 'respect' in your marriage as well. I think passion blooms from the seed of respect. Respect that you have for yourself, the respect you have for your partner, and the respect you have for your marriage. If any one of those 'respect' areas is lacking, from YOU first, and then from your spouse, you are facing a passionless marriage.
If you can restore that, with you and your partner, I think you are well on your way to restoring whatever passion may be missing.
